var documentsInAllPeriods = documents.Where(d => periods.All(p =>
d.Date >= p.DateFrom && d.Date <= p.DateTo));
(Note you can change All
to Any
if you want the documents in any period rather than the documents in every period.)
题
Let's say I have these two entities :
Then, consider this expression, in which d represents a Document and p represents a Period, that is used to filter a Document collection to return only those who are part of a given Period :
d => d.Date >= p.DateFrom && d.Date <= p.DateTo
The problem is, given a collection of Period entities, how could I build a lambda expression which represents a concatenation of multiple expressions like the above expression, so it gives :
d =>
(d.Date >= p1.DateFrom && d.Date <= p1.DateTo)
&& (d.Date >= p2.DateFrom && d.Date <= p2.DateTo)
&& (d.Date >= p3.DateFrom && d.Date <= p3.DateTo)
&& ...
I want the result to be a lambda expression that I can further combine to other conditions before filtering my Document collection.
解决方案
var documentsInAllPeriods = documents.Where(d => periods.All(p =>
d.Date >= p.DateFrom && d.Date <= p.DateTo));
(Note you can change All
to Any
if you want the documents in any period rather than the documents in every period.)
其他提示
Assuming the collection of period entities (periods) is available for the lambda expression:
(d) =>
{
bool cond = false;
foreach(Period p in periods)
{
// check period
// return earlier if condition not met
}
return cond;
}